A. Field of the Invention
This invention relates to a telephone control interface system for use with digital telephones that are coupled to programmable computer control.
B. Related Art
A computer controllable telephone typically includes at least two ports: a telephone line interface for connection with a telephone network, and a data communication interface for communication with a computer. For example, a telephone such as the ROLMphone (R) 244PC includes a telephony port for providing connection to a private branch exchange (PBX) and an asynchronous data communication port for providing connection to a computer. The computer communicates with the phone via the data communication port in a manner similar to that in which it would communicate with a modem. Applications executing on the computer can control the phone, accessing the various PBX telephony features by way of a command set. A typical application would be, for example, an auto-dialer.
An increasingly popular network architecture is the integrated services digital network (ISDN). This network provides many features, including enhanced telephony services. The enhanced telephony services provide flexible control of telephone calls and communication of status information about the telephone. Examples of ISDN call status information include call state, calling number, available features and other events. By communicating the ISDN call status information to a host computer, via a telephone's data communications port, the operation of the telephone can be automated by a computer application program.
Conventionally, the telephone's data communications port will pass the ISDN call status information to the host computer's application program with no modification. This places the burden on the application to filter unwanted events. Application based filtering requires additional processing time and real time usage of the host computer where the application is running. Under this environment, telephony application programs must often be able to handle events that are not pertinent to the desired task.